What does "dragon to mouse" mean here?
The phrase is juxtaposing the awesome political, military, and economic might of China, against the comparatively meager stature of their rivals. Following the phrase "behind closed doors and bilaterally..." which means that it is a one-on-one "negotiation," with nobody else there to witness the scenario or to stand up for the less powerful entity. The "dragon to mouse" metaphor is highlighting this highly lop-sided power dynamic. Just picture a dragon negotiating with a mouse in a dark room and that pretty much says it all.